Cover the grass that is growing there with newspaper or cardboard and cover that with a mixture of the mineral portion of soil and compost in a ratio so the compost equals about 6 to 8 percent of that mix.

Thanks for the response. I will do tht then. thanks.

Yup -- if you choose newspaper, use at least 4 layers, and wetting it helps too.
Unless the grass you have is quack grass, in which case it will grow up though anything. YOu'll find out.

If there are leaves in there already just throw the dirt on top.
Make sure it is enough as even quack grass has trouble you bury the live plant deep enough, verses seeding with chopped up rhizomes from trying to dig it out.

I have buried random quack grass, and find that if it does pop through, just digging down and using systemic weed killer can kill it.
If the entire lawn is quack grass, you are dooooooomed.

No, no, Rpr -- if the entire lawn is quack grass, digging it becomes spiritual practice, with guarantee of enlightenment as soon as you dig out the last rhizome.